In tomographic methods, particularly in the field of computed tomography or NMR tomography, it is advantageous to apply contrast media in order to display specific body regions because of the low contrasts in the display that occur there, and thereby to obtain a more contrasting image of these body regions. However, contrast media mostly have the disadvantage that they are biologically incompatible and that their dose therefore has to be kept as low as possible. Because of the biological variability of the bodies under examination, however, it is impossible to make a sufficiently accurate and generally valid statement as to how the concentration profile of a specific contrast medium dose will develop over time at an observed location in the body. It is therefore necessary in the case of each body under examination to make a test injection of a contrast medium or test bolus dose so as to observe the effect thereof, in particular the subsequent time profile of the concentration values at the location of interest in the body to be examined.
In the case of application in association with a CT examination, the concentration is measured indirectly over a specific time period after the test bolus injection and with the use of the smallest possible radiation doses, this being done via the changes in the HU values resulting there. Since only the imaging effect of the contrast medium is of interest, and there is a linear relationship between the imaging effect and concentration of the contrast medium, a statement on the absolute concentration of the contrast medium remains open and trivial. Again, the resolving power of the images of such a test examination remains slight.
It is known to use knowledge of the effect of such a test bolus dose with the aid of a Fourier transformation as a basis for preliminary calculation of the effect of a correct contrast medium dose, and thus for determining the absolutely necessary dose of contrast medium.